Communicating Transaction Types Between Agents in a Computer System Using Packet Headers Including Format and Type Fields

1. An apparatus comprising: a general input/output communication port to implement a communication stack including a physical layer, a data link layer and a transaction layer, the transaction layer to assemble a packet header for a transaction packet, the packet header to include: a format field to indicate whether the transaction packet includes a data payload and to specify a size of the packet header; and a type field to specify a transaction type, the transaction type to be selected from a group consisting of: a memory request, an input/output request, a configuration request and a message request, wherein the format field and the type field together indicate a transaction layer packet format associated with a packet type.

2. The apparatus of claim 1 , wherein the format field and the type field are located in the first byte of the packet header, and wherein the packet type is selected from a group consisting of a memory read request, a memory write request, an input/output (IO) read request, an IO write request, a configuration read, a configuration write, a message request, a message request with data, a message for advanced switching, a completion without data, a completion with data, and a completion for lock memory read.

3. An apparatus comprising: a general input/output communication port to implement a communication stack including a physical layer, a data link layer and a transaction layer, the transaction layer to disassemble a packet header for a packet to be received at the general input/output communication port, the packet header to include: a format field to specify whether the packet includes a data payload and to specify a size of the packet header; and a type field to specify a message transaction type in response to holding a message value and to specify a non-message request transaction type in response to holding a request value, an additional field to hold message code information in response to the type field holding the message value and to hold byte enable information in response to the type field holding the request value.

4. The apparatus of claim 3 , wherein the type field is further to specify a completion transaction type in response to holding a completion value, and wherein the additional field is to hold completion status information in response to the type field holding the completion value.

5. The apparatus of claim 3 , wherein the packet header is also to include a length field to specify the length of the data payload in response to the format field specifying the packet includes a data payload.

6. The apparatus of claim 5 , wherein the transaction layer is to compare the length of the data payload specified in the length field to an actual length of the data payload and to treat the request transaction packet as malformed request transaction packet based on the actual length not matching the length of the data payload specified in the length field.

7. A system comprising: a transmitting device to include a general input/output communication port to implement a communication stack including a physical layer, a data link layer and a transaction layer, the transaction layer to assemble a packet header for a transaction packet , the packet header to include: a format field to indicate whether the transaction packet includes a data payload; a type field to indicate a transaction type, the transaction type to include at least one selected from the following group of: a memory request, an input/output request, a configuration request and a message request, wherein the format field and the type field together specify the format for the packet header; a length field to indicate a length of the data payload in response to the format field indicating the transaction packet includes the data payload, and an extension field to be disposed between the type field and the length field capable of extending the type field or the length field in response to the transaction type; and a receiving device to receive the packet header from the transmitting device the receiving device to implement the communication stack that includes the data link layer, the physical layer and the transaction layer, wherein the transaction layer is to disassemble the packet header.

8. The system of claim 7 , wherein the packet header is further to include an additional field to hold additional information, and wherein the transaction layer is to determine a type of the additional information to be held in the additional field based on the format and the type field together, the transaction layer to determine a type of the additional information to be held in the additional field based on the format and the type field together comprises: determining the additional field includes a byte enable field to hold byte enable information in response to the format field and type field together indicating the transaction packet is a request packet, determining the additional field includes a completion status field to hold competition status information in response to the format field and type field together indicating the transaction packet is a completion packet, and determining the additional field includes a message code field to hold message code information in response to the format field and type field together indicating the transaction packet is a message packet.

9. The system of claim 8 , wherein the format field and the type field are located in the first byte of the packet header.

10. An apparatus comprising: a general input/output communication port to implement a communication stack including a physical layer, a data link layer and a transaction layer, the transaction layer to assemble a packet header for a packet to be transmitted on a serial point-to-point link, the packet header to include: a first field to indicate a size of the packet header and to indicate whether the packet is to include a data payload; a second field to indicate a transaction type of the packet; and a third field to represent a length of the data payload, in response to the first field indicating the packet is to include a data payload.

11. The apparatus of claim 10 , wherein the packer header is also to include a fourth field to include a first type of information in response to the first and second field in combination representing a first packet type and to include a second type of information in response to the first and the second field in combination representing a second packet type.

12. The apparatus of claim 11 , wherein the first type of information includes byte enable information, the first packet type includes a non-message request packet type, the second type of information includes message code information, and the second packet type includes a message type.

13. The apparatus of claim 11 , wherein the fourth field, in response to the first and the second field in combination representing a third packet type, is to include a third type of information, and wherein the third packet type includes a completion packet type and the third type of information includes completion status information.

14. The apparatus of claim 13 , wherein byte enable information includes beginning of a data payload information and end of data payload information, the beginning of a data payload information to indicate whether a first number of bytes at a beginning of the data payload are enabled and the end of data payload information to indicate whether a second number bytes at the end of the data payload are enabled.

15. The apparatus of claim 11 , wherein the packet header is also to include a fifth extension field to be associated with the second field in response to the first and the second field in combination representing the first packet type, and to be associated with the third field in response to the first and the second field in combination representing the second packet type.

16. The apparatus of claim 15 , wherein the first packet type is selected from a group consisting of a locked memory read request, an I/O read request, and I/O write request, a configuration read type 0 , a configuration write type 0 , a configuration read type 1 , a configuration write type 1 , a completion without data, and a completion for locked memory read, and wherein the second packet type is selected from a group consisting of a completion with data, a memory read request, and a memory write request.

17. The apparatus of claim 15 , wherein the packet header is also to include an additional field, wherein the additional field is selected from a group consisting of an address field, a requester ID field, a tag field, an attribute field, a completer ID field, and a virtual channel ID field.

18. The apparatus of claim 10 , wherein first field further indicates if the data payload is four-byte naturally aligned and limited in size by a maximum data payload size, in response to indicating the packet is to include a data payload.